Study On Energy Efficiency Of Wet Flue Gas Desulphurization Tower Under Ultra-low Emission Conditions

In December 11,2015,the EPD,the EB and the DRC issued the "Comprehensive implementation of ultra-low emission and energy saving retrofit plan for coal-fired power plants".By 2020,all coal-fired power plants with reformed conditions in the country strive to achieve ultra-low emissions.The strict control of pollutants is bound to lead to the increase of the cost of emission reduction.As the high energy consumption and environmental protection equipment of the plant,the WFGD tower has the huge slurry flow and the flue gas system resistance to increase the coal consumption of power supply of the plant by about 3?6g/(kW · h).Therefore,it is urgent to study the energy efficiency of the WFGD tower under the ultra-low emission conditions,and form a certain evaluation and analysis method.In this paper,a model of heat and mass transfer in a WFGD tower is built on the basis of the double model theory and the A-S turbulence droplet evaporation model.The Realizable k-epsilon turbulence model is used to describe the turbulent flow of the flue gas and the DPM model to describe the slurry droplet movement.A numerical simulation study was carried out on a W tower of a 150 MW ultra-low emission plant.The simulation results show that:(1)L/G and the velocity of flue gas are the key parameters affecting the heat and mass transfer process in the tower.(2)in terms of heat transfer,the area between the inlet of the tower and the first layer of the spray layer is defined as the "core heat transfer zone".As L/G increases,the cooling process of the flue gas decreases gradually.The main area of heat transfer is transferred from the upper side to the lower side of the alloy tray.As the flue gas velocity increases,the cooling process increases,and the high temperature region is extended to the upper side and the offside of inlet,and the gas and liquid demarcation is extended to the offside of inlet.(3)in mass transfer,the desulfurization efficiency(?SO2)increases with the increase of L/G.After L/G is more than 22 L/Nm3,?SO2 is basically unchanged.?SO2 has a positive correlation with the cross section flue gas velocity,and the two phase turbulence's promotion to mass transfer of SO2 is bigger than flue gas's retention time.The influence of the inlet SO2 concentration on ?SO2 is very small.(4)synergistic equipment can obviously improve the process of heat and mass transfer of short circuit flue gas.In this paper,energy consumption is based on electricity consumption.The consumption of limestone and fresh water consumption are converted into electricity consumption,and the energy consumption of the tower is unified on electricity consumption.Considering energy consumption and desulfurization performance,3 energy efficiency analysis indexes(IC/O?IS/C and IC/S)were put forward according to different analysis strategies.The energy efficiency analysis method of WFGD tower was studied.In this paper,TC/S is selected as the index of energy efficiency analysis.In this paper,the influence of operating parameters,flue gas parameters and technical parameters on the energy efficiency of WFGD towers under ultra-low emission conditions is studied by using IC/S as dependent variable.The results of numerical simulation and running data show that:(1)IC/S decreases with the velocity of flue gas and increases linearly with the increase of L/G.(2)IC/S decreases with the increase of SO2 concentration,and these two parameters are approximately inverse proportional function,but the inlet S02 concentration is not the direct influence factor of IC/S.(3)the mass flow of SO2 is the dominant factor of IC/S.IC/S decreases with the increase of mass flow of SO2.When the mass flow of SO2 is greater than 1200kg/h,the change trend gradually tends to be slow.Multiple clear IC/S change curves can be obtained according to the number of running spray layers,and the distance between the curves represents the additional energy consumption from the additional running spray layer.(4)the effect of unit load on IC/S is very small,and there is no clear correlation between them in actual operation.